Laser assemblies, including side fire laser assemblies, may be used for laser-based surgical procedures, for example, to deliver laser energy of a specific wavelength at a specific pulse rate to remove tissue through vaporization. Such procedures may be performed in an aqueous environment, for example, within water.
FIG. 1 shows a conventional side fire laser assembly 100 including a side fire optical fiber 130. An end 132 of the optical fiber 130 may be polished at a specific angle such that energy is emitted to a side of the optical fiber 130, as opposed to the end. To permit the laser to emit energy at the correct angle, an air interface is provided at the polished end 132 of the optical fiber 130. As shown in FIG. 1, an air gap 160 is formed in the conventional laser assembly 100 when a capillary tube 150 is fused to the optical fiber 130 and an end 152 of the capillary tube 150 is heated until the end of the capillary tube 150 collapses, thereby forming the air gap 160. A metal cap 170 may be placed over the end 152 of the capillary tube 150. Adhesive 180 may be used to adhere the metal cap 170 to the capillary tube 150 and to adhere the capillary tube 150 and the metal cap 170 to an outer layer 138 of the optical fiber 130. The metal cap 170 helps to protect and reinforce the capillary tube 150 during energy delivery through the laser assembly 100.
During a procedure, such as Holmium laser ablation of the prostate (HoLAP), this conventional laser assembly 100 may be used to deliver laser energy to ablate prostatic tissue for the purpose of alleviating symptoms of Benign Prostatic Hyperplasia (BPH). BPH is a common condition in which the prostate becomes enlarged with aging, which can squeeze the urethra and cause irritation or obstruction of urine flow. Laser-based surgical procedures employing side-firing optical fibers and high-power lasers may be used to remove obstructing prostate tissue, e.g., associated with BPH. The conventional laser assembly 100 may include a laser (not shown), such as a Holmium:YAG (Ho:YAG) laser, that may generate the laser energy delivered through the optical fiber 130. Holmium laser treatment is a minimally invasive alternative to transurethral resection of the prostate (TURP).
The conventional laser assembly can operate at 100 W of average power. This means that, for every second, 100 J (joules) of energy can pass through the optical fiber. The laser assembly can operate in a pulse mode with a pulse rate of 50 Hz and a pulse duration of 200 μs (microseconds). Each pulse therefore can deliver 2 J (100 J/50 Hz) and 10,000 W of power (2 J/200 μs=2 J/0.2×10−3 s=10×103 W). This pulsed Holmium energy may react with the water surrounding the laser assembly 100 and may create vapor bubbles upon exiting the optical fiber 130 and the capillary tube 150. These vapor bubbles may collapse back violently, which may subject the optical fiber 130 and the capillary tube 150 to significant forces. At a high pulse rate (e.g., 50 Hz), these forces may cause the optical fiber 130 to vibrate, which may in turn break down the brittle adhesive 180 holding the metal cap 170 onto the capillary tube 150. Over time, the adhesive 180 may break loose, may burn up due to the heat generated during energy delivery, and/or may fall out of the metal cap 170. As a result, a substantial gap may be formed between the metal cap 170 and the capillary tube 150 due to the absence of the adhesive 180. The gap between the capillary tube 150 and the metal cap 170 may cause the capillary tube 150 to vibrate against the rigid surfaces of the metal cap 170 as the laser assembly 100 continues delivering the pulses of laser energy. The vibrations of the capillary tube 150 against the metal cap 170 may cause the capillary tube 150 to fracture and may cause pieces of the capillary tube 150 to break away. As a result, the capillary tube 150 is rendered unusable and must be replaced. Accordingly, a need exists for a laser assembly that can withstand high vibrations.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.